For the past twenty years, optically pumped solid state lasers have found widespread application as a source of coherent radiation. In applications that require lasers that have very short cavity lengths (hereafter referred to as "microlasers"), the preferred solid state gain medium has been neodymium doped yttrium aluminum garnet (Nd:Y.sub.3 Al.sub.5 O.sub.12) (hereafter referred to as "Nd:YAG") because of the composition's advantageous physical characteristics. 1% Nd:YAG has a maximum Nd-ion absorption coefficient at pump wavelengths between 0.8 to 0.82 micrometers of approximately 8 inverse centimeters. This allows a laser that employs Nd:YAG as the solid state gain medium to have short cavity lengths, as short as 2.5 millimeters, and yet still have 99% pump light absorption. Moreover, the stimulated emission cross section of Nd:YAG for the transition at 1.06 micrometers is relatively high, 4.6.times.10.sup.-19 centimeters.sup.2. This translates into low lasing thresholds and high gain which are both important considerations for microlasers which have a low gain length compared to conventional solid state lasers.
Nonetheless, despite Nd:YAG's advantageous physical characteristics, research into the physical characteristics of other complex host crystal-ion combinations for use as solid state gain mediums in lasers is continuing.